An automatic transfer switch is used for selectively connecting a preparatory power to a load side with the preparatory power being used when a commercial power has a problem. The automatic transfer switch consists of an air circuit breaker which automatically disconnects a commercial power when a commercial power has a problem, and another air circuit breaker which automatically disconnects an emergency power.
So, as shown in FIG. 1, a connection and disconnection are separately performed between the commercial power and the preparatory power in the conventional automatic transfer switch.
When a commercial power has a problem, a preparatory power should be connected at the time when a commercial power is disconnected for a reliable power supply. However, the connection and disconnection in the conventional automatic transfer switch are separately performed, so that it is impossible to fast and reliably supply power. Since the air circuit breaker should be separately provided for a commercial power and a preparatory power, respectively, it costs too much, and the installation area disadvantageously increases.
When a manufacturing facility, which operates with power, is damaged or has a problem, it is needed to disconnect both the commercial power and the emergency power. In this case, since the commercial power and the preparatory power are separately controlled, it is impossible to concurrently disconnect the commercial power and the preparatory power. When the contact points of a commercial power or emergency power are connected, a handle is installed at an automatic transfer switch is manually operated. Here, since each handle is operated with a manual force, it is not easy to properly operate the handles. There are many potential error portions such as in a connection state of an external interlock and a housing.